What is Vitamin D2: Uses, Warnings & Interactions

Medically reviewed by Ashley Wong, Pharm. D.
Licensed Pharmacist
Updated May 14, 2025  •  Published Dec 30, 2020
Fact Checked

Ergocalciferol, also known as vitamin D2, is a prescription vitamin used to treat and prevent conditions caused by low levels of calcium and phosphate in the body, such as rickets, osteomalacia, and certain types of hypoparathyroidism.

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Vitamin D2 overview

BRAND NAMES:

  • Calcidol, Calciferol, Drisdol

Generic Names:

  • Vitamin D2 (Ergocalciferol)

Uses:

  • Increases the amount of vitamin D in your body. Also treats problems caused by not having enough calcium in the body (such as rickets). Ergocalciferol is a form of vitamin D.

Therapeutic Classes:

  • Vitamin D analog

Forms:

  • Capsule, Liquid Filled Capsule, Liquid, Tablet

How it’s taken:

  • By mouth

What is Vitamin D2 used for?

Ergocalciferol is a form of vitamin D used to treat and prevent rickets and osteomalacia. It is also used to treat low levels of calcium or phosphate caused by hypoparathyroidism, pseudohypoparathyroidism, and familial hypophosphatemia. Ergocalciferol increases the levels of calcium and phosphorus in the body. It is indicated for use by adults and children.

Key takeaways

  • Ergocalciferol will only work if you are consuming adequate calcium in your diet. Calcium-rich foods include dairy products, such as milk, yogurt, and cheese, spinach, collard greens, tofu, and certain juices. Ask your healthcare provider how many servings of calcium-rich foods you should eat each day. 

  • You may take ergocalciferol with or without food at any time of day. Taking it at the same time each day is recommended as it will keep a consistent amount of medication in your body. 

  • Your healthcare provider may order blood tests while you take ergocalciferol. Depending on the results, your healthcare provider may adjust your dosage of ergocalciferol. 

  • Take ergocalciferol exactly as prescribed. Taking too much of the medication can increase your risk of side effects, such as nausea, constipation, and loss of appetite. On the other hand, taking too little of the medication or missing doses can make it less effective at treating your condition.

What form(s) does Vitamin D2 come in

  • Capsule

    • 1.25 mg (50,000 IU)

  • Tablet

    • 10 mcg (400 IU)

    • 50 mcg (2,000 IU)

  • Liquid solution

    • 200 mcg/mL (8,000 IU/mL)

What are common Vitamin D2 doses?

  • The dosage of the prescription-strength ergocalciferol depends on the condition being treated.

    • Vitamin D resistant rickets: 12,000 to 500,000 IU by mouth daily

    • Hypoparathyroidism: 50,000 to 200,000 IU by mouth daily along with calcium supplementation

If you’re taking the over-the-counter (OTC) version of ergocalciferol, ask your healthcare provider or pharmacist what dosage you should take.

Common Vitamin D2 prescriptions

  • Vitamin D (Ergocalciferol)
    60 capsules bottle

  • Vitamin D (Ergocalciferol)
    1.25 mg(50000 ut) capsule

  • Vitamin D (Ergocalciferol)
    50000unit capsule

How to take Vitamin D2

  • Your doctor will tell you how much medicine to use. Do not use more than directed.

  • Follow the instructions on the medicine label if you are using this medicine without a prescription.

  • You may take this medicine with or without food.

  • Use the dropper that comes with the oral liquid to measure your dose. Do not use a kitchen spoon or measuring tool, as these can provide an inaccurate dose.

What to do if you miss a dose of Vitamin D2

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.

  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Vitamin D2 contraindications

  • You should not use this medicine if you have had an allergic reaction to vitamin D.

  • You should also not take this medication if you have the following conditions:

    • Hypercalcemia (high blood calcium levels)

    • Malabsorption syndrome (a condition where your body can’t absorb nutrients as well as it should)

    • Hypervitaminosis D (high blood vitamin D levels)

Vitamin D2 warnings

  • Make sure your healthcare provider knows if you are pregnant or breastfeeding.

  • Make sure your doctor knows about all health problems that you have.

Vitamin D2 interactions

  • Avoid antacids that contain aluminum (such as Amphojel®, Maalox®, Mylanta®) while using this medicine.

  • Make sure your doctor knows if you are also using carbamazepine (Tegretol®), cholestyramine (Questran®), mineral oil, orlistat (Xenical®), phenobarbital (Luminal®, Solfoton®), or a diuretic or "water pill" (such as hydrochlorothiazide [HCTZ]).

Vitamin D2 side effects

Serious side effects

  • Muscle aches, stiffness, weakness

  • Kidney problems, which can cause changes in urination, high blood pressure

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

Less serious side effects

  • Constipation

  • Nausea and vomiting

  • Loss of appetite

  • Weight loss

  • Pale skin

  • Tiredness 

If you develop any serious, worsening, or persistent side effects, talk with your healthcare provider right away. 

Sources:

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Medically reviewed by Ashley Wong, Pharm. D.
Licensed Pharmacist

Ashley Wong, Pharm.D., has worked for healthcare companies where she translated complex drug information into easy-to-understand language for patients. She also served as a Senior Medical Information Specialist at a medical communications company, where she delivered clinically accurate drug information to healthcare providers and patients and compiled adverse event reports in accordance with the FDA's reporting guidelines.

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